1. Field of the Invention
The invention relates generally to devices and methods for sizing, stabilizing and/or reducing the circumference of an anatomical structure, such as a heart valve, and more particularly, to such devices and methods that can also deliver certain suture support elements to the anatomical structure with a consistent, uniform, predetermined spacing.
2. Description of Related Art
Although current artificial and prosthetic heart valves can greatly improve the condition of a patient, these devices present serious drawbacks, such as thrombogenicity (tendency towards thrombus formation and subsequent detachment with embolization) and limited durability secondary to tissue structure failure, i.e. SVD (structural valve deterioration).
Other complications can also occur, such as noise, interference with hemodynamics, especially in smaller sizes, hemolysis (destruction of blood elements), endocarditis (valve infection) and dehiscence of the valve. Because of the risk of embolism, the majority of patients who receive mechanical artificial heart valves must take anticoagulant medication for life, with the concomitant risk of hemorrhage and necessary change in lifestyle. Patients who receive tissue bioprostheses and commercially available annuloplasty rings generally must take anticoagulative medication for about three months.
Different and more recent developments in the field of cardiac surgery have included attempts to surgically repair, instead of replace, diseased heart valves and other vascular tissue. A variety of surgical maneuvers and procedures exist for this purpose. Many cardiac surgeons consider this type of reconstructive surgery superior to valve replacement in many respects, although it is generally more technically difficult and time-consuming to perform and not always possible in every patient.
Among the variety of reconstructive surgical procedures, valve annuloplasty is the most frequently performed in the tricuspid and mitral valves. A valve annuloplasty procedure selectively reduces the size of a dilatated valve annulus. A number of prosthetic rings exist for this purpose, such as the commercially available Carpentier ring (distributed by American Edwards Laboratories).
The Carpentier method of valvuloplasty employing the Carpentier ring is disclosed in the product pamphlet "Prosthetic Rings and Accessories for Tricuspid and Mitral Valvuloplasty", produced by American Edwards Laboratories in December, 1985. See also U.S. Pat. Nos. 5,061,277 and 4,917,698 to Carpentier for related discussions.
Commercially available annuloplasty rings have a number of drawbacks. First, they are expensive. Second, unless they are either rigid or sutured to the tissue annulus while still attached to a rigid holder, they may suffer an unpredictable degree of longitudinal shortening within the confines of each mattress suture used to secure the ring to the tissue annulus. (Even a running suture preferred by a few surgeons is still likely to produce some longitudinal shortening of the ring.) Thus, they may fail to provide a precise, predictable, reproducible annuloplasty. Further, without a rigid element present when the suture is tied, each suture is necessarily tied with variable and unpredictable degrees of tension by the operating surgeon.
Third, most annuloplasty rings are completely circumferential, committing the operating surgeon to placing sutures in the anterior annulus where dilatation rarely occurs and where a tissue tear from inexact suture placement can produce a hole in the aortic-mitral curtain, resulting in significant mitral regurgitation. Fourth, a rigid mitral ring, because it is pre-shaped to an oval configuration, must be precisely placed and is not very forgiving with inexact placement. Fifth, a rigid tricuspid ring can dehisce if not made to conform to the slightly spiral, nonplanar shape of the tissue annulus. Sixth, any rigid ring impedes the normal flexibility of the tissue annulus during ventricular contraction. Seventh, all commercially available rings, which generally come only in a few generic sizes and shapes, are necessarily approximations of the exact size and shape of the original mitral valve orifice and therefore are usually not truly precise. Finally, ring implantation with conventional surgical technique is a significantly invasive procedure.
A need exists, therefore, for an apparatus and method which provide a customized annuloplasty, tailored to the needs of the original size and shape of each unique mitral, tricuspid, or other orifice and of specific pathophysiological situations, including but not limited to a limited annuloplasty of any valve annulus, a subtotal annuloplasty of any valve, or a complete annuloplasty of any valve annulus. A need also exists for an apparatus and method which allow the repaired vascular structure to retain its flexibility in all planes while preventing further dilatation or circumferential lengthening of the tissue annulus or vascular structure. Additionally, a need exists for an apparatus and method that are precise, customizable, simple to use and manufacture, low-cost, and, as needed, minimally invasive.